Biodegradable T-cell Activation device

ABSTRACT

A biodegradable device for activating T-cells includes a biodegradable support and a binder attached to the biodegradable support, the binder having reactivity to one or more agents capable of binding to a T-cell surface antigen.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of U.S.provisional patent application Ser. No. 60/547,966, filed Feb. 26, 2004,the content of which is hereby incorporated by reference in itsentirety.

The present application is a continuation-in-part of and claims priorityof U.S. patent application Ser. No. 11/066,133, filed Feb. 24, 2005, thecontent of which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

This invention relates to a biodegradable device for activating,expanding and differentiating T-cells for use in cell therapy treatmentprotocols.

BACKGROUND

Cell therapy methods have been developed in order to enhance the hostimmune response to tumors, viruses and bacterial pathogens. Cell therapymethods often involve the ex-vivo activation and expansion of T-cells.Examples of these type of treatments include the use of tumorinfiltrating lymphocyte (TIL) cells (see U.S. Pat. No. 5,126,132 issuedto Rosenberg), cytotoxic T-cells (see U.S. Pat. No. 6,255,073 issued toCai, et al.; and U.S. Pat. No. 5,846,827 issued to Celis, et al.),expanded tumor draining lymph node cells (see U.S. Pat. No. 6,251,385issued to Terman), and various other lymphocyte preparations (see U.S.Pat. No. 6,194,207 issued to Bell, et al.; U.S. Pat. No. 5,443,983issued to Ochoa, et al.; U.S. Pat. No 6,040,177 issued to Riddell, etal.; U.S. Pat. No. 5,766,920 issued to Babbitt, et al.).

T-cells must be activated in order to proliferate, perform effectorfunctions and produce cytokines (Liebowitz, Lee et al. 1998). T-cellsrequire direct contact with antigen presenting cells (“APC”) foractivation. APC convert protein antigens to peptides and then presentpeptide-MHC complexes in a form that can be recognized by T-cells. Theinteraction of the peptide-MHC complex on the APC and the T-cellreceptor (“TCR”) on the surface of the T-cell usually provides the firstof the two signals required for activation. The second of the twosignals required for activation is usually provided by membrane-bound orsecreted products of the APC.

Due to the difficulty in maintaining large numbers of natural APC incultures and in identifying disease-associated antigens and controllingthe processing and presentation of these antigens to T-cells by naturalAPC, alternative methods have been sought for ex-vivo activation ofT-cells for use in cell therapy. One method is to by-pass the need forthe peptide-MHC complex on natural APC by instead stimulating the TCRwith polyclonal activators, such as immobilized or cross-linked anti-CD3monoclonal antibodies (mAbs) to provide the first signal to T-cells.Other methods take advantage of the secondary T-cell activation pathwayto provide the first signal, such as the use of immobilized orcross-linked anti-CD2 mAb.

The combination of anti-CD3 mAb (first signal) and anti-CD28 mAb (secondsignal) is most commonly used to substitute for natural APCs in inducingT-cell activation in cell therapy protocols. The signals provided byanti-CD3 and anti-CD28 mAbs are best delivered to T-cells when theantibodies are immobilized on a solid surface such as plastic plates(Baroja, Lorre et al. 1989; Damle and Doyle 1989) or sepharose beads(Anderson, Blue et al. 1988) (see also U.S. Pat. No. 6,352,694 issued toJune, et al.).

A method for immobilizing anti-CD3 and anti-CD28 mAb on tosyl-activatedparamagnetic beads with a 4.5 micron diameter and the subsequent use ofthese beads to stimulate T-cells to proliferate and producepro-inflammatory cytokines has been described (Levine, Bernstein et al.1997). It has also been shown that T-cells activated with these beadsexhibit properties, such as cytokine production, that make thempotentially useful for adoptive immunotherapy (Garlie, LeFever et al.1999; Shibuya, Wei et al. 2000). These beads are now commerciallyavailable from Dynal, NS (Oslo, Norway) under the trade name Dynabeads®CD3/CD28 T-cell Expansion.

The use of paramagnetic beads with immobilized mAbs for expansion ofT-cells in cell therapy protocols requires the separation and removal ofthe beads from the T-cells prior to patient infusion. This is a verylabor-intensive process and results in cell loss, cell damage, increasedrisk of contamination and increased cost of processing. Because of thetight association of the immobilized mAbs on the beads with thecorresponding ligands on the surface of the target T-cells, the removalof the beads from the T-cells is difficult. The bead:cell conjugates areoften separated by waiting until the T-cells internalize the targetantigens and then by using mechanical disruption techniques to separatethe beads from the T-cells. This technique can cause damage to theT-cells and can also cause the ligated antigens on the T-cells to beremoved from the cell surface for a period of time (Rubbi, Patel et al.1993). In addition, highly activated T-cells are most desirable for usein cell therapy protocols and T-cells often lose this desirable propertyduring the 24-72 hour waiting time for the T-cells to internalize thetarget antigens.

The process of removing the paramagnetic beads after separation from theT-cells requires the passing of the cell/bead solution over a magnet.This process can greatly reduce the quantity of beads remaining with theT-cells, but does not completely eliminate the beads. This incompletebead removal results in some beads being infused in patients which cancause toxic effects. The magnetic bead removal process also reduces thenumber of T-cells available for therapy, as many T-cells remainassociated with the paramagnetic beads even after the waiting time andmechanical disassociation, and are thus removed with the beads in themagnetic field. Some cell loss also occurs when T-cells that may not bebound to the beads become entrapped by beads pulled to the surface nextto the magnetic source.

SUMMARY OF THE INVENTION

The present invention includes a biodegradable device for activatingT-cells including a biodegradable support and a binder attached to thebiodegradable support, the binder having reactivity to one or moreagents capable of binding to a T-cell surface antigen.

The present invention also includes a method for activating T-cells, themethod comprising attaching one or more T-cell activators to apopulation of T-cells and mixing the T-cells with a biodegradablesupport with an attached binder having reactivity to the T-cellactivators.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention utilizes a biodegradable support material coatedwith a first material capable of immobilizing or cross-linking one ormore second materials with reactivity for structures on the surface of aT-cell. The biodegradable nature of the support material eliminates theneed to employ a process to separate and remove the support from theT-cells prior to infusion into a patient.

Use of biodegradable materials in medical applications are well known.These materials have been used for encapsulation of proteins forvaccination and controlled drug release (see for example U.S. Pat. No.6,572,894 issued to Rossling, et al.). Biodegradable materials have alsobeen formulated for use as sutures (see e.g., Bezemer at al., U.S. Pat.No. 6,500,193), and have been used in tissue engineering applications(see e.g., Vert et al. in U.S. Pat. No. 4,279,249 and Slivka, et al inU.S. Pat. No. 6,511,511) and used as implants (see e.g., Leatherbury, etal. in U.S. Pat. No. 6,514,286). The physical and chemical properties ofthe biodegradable material for use in these prior art applicationsdiffer significantly from the requirements of the present invention.Prior art applications require slow, controlled degradation andencapsulation of active ingredients and/or high tensile strength andstability. The application of the present invention requires rapiddegradation which does not need to be at a controlled rate and also doesnot require high tensile strength. Second, materials only need to becross-linked for a period of 4 to 24 hours in order to deliver a signalto T-cells. In addition, the present invention does not requireencapsulation of an active ingredient as in most prior art methods usingbiodegradable microspheres.

The biodegradable material selected for use in the present inventionmust be non-toxic and non-antigenic in humans, and preferably must becapable of being delivered to humans parenterally, preferablyintravenously. The biodegradable material can be derived from natural orsynthetic materials that degrade in biological fluids. It is preferablethat degradation occur using non-enzymatic means. For purposes of thepresent invention, biological fluids include cell culture media andblood. The biodegradable material must degrade rapidly (i.e., within amonth, preferably within 2 weeks, more preferably within 1 week, andmost preferably within 3 days). The biodegradable material degradationproducts must produce non-toxic by-products that can be metabolizedand/or excreted via normal physiological pathways.

It is also preferable that biodegradable materials used in formulatingthe device of the present invention do not utilize organic solvents inthe manufacturing process, as these solvents pose a health risk onlong-term exposure in humans. However, a preferred embodiment is theformulation of microspheres from synthetic polymers of which virtuallyall fabrication processes require use of an organic solvent such asdichloromethane. If organic solvents are utilized in the manufacture ofthe biodegradable supports, attempts should be made to reduce the amountof residual solvent in the final formulation. Acceptable residualsolvent concentrations are determined by regulatory agencies. Forexample, ICH (International Conference on Harmonization) guidelines setthe maximal permissible dichloromethane levels in the blood at 6 mg/day.

Examples of suitable natural materials for use as biodegradable supportsinclude proteins such as collagen, gelatin and albumen andpolysaccharides such as starch, dextran, inulin, cellulose andhyaluronic acid.

Examples of synthetic materials for use as biodegradable supportsinclude aliphatic polyesters, such as poly(lactic acid) (PLA),poly(glycolic acid) (PGA), copolymers of PLA and PGA (PLGA) orpoly(carprolactone) (PCL), and polyanhydrides. These materials have beenwidely used as biodegradable polymers in medical applications. Syntheticpolymers in general offer greater advantages over natural materials inthat they can be tailored to give a wider range of properties and havemore predictable lot-to-lot uniformity.

The factors which affect the physical properties and performance ofbiodegradable polymers are well known. These factors include monomerselection, initiator selection, process conditions and the presence ofadditives. These factors in turn influence the polymer's hydrophilicity,crystallinity, melt and glass transition temperatures, molecular weightdistribution, end groups, sequence distribution (random vs. blocky) andthe presence of residual monomer additives.

In general, for the purposes of the present invention, polymers shouldbe selected for high hydrophilicity, polymers may be eithersemicrystalline or amorphous, preferably amorphous, with a glasstransition temperature that is preferably well above 37° C., allowingthe polymer to act more like a glass than a rubber at body temperature.Polymers should have a low molecular weight distribution and lowinherent viscosity for accelerated degradation, and the preference isfor random over blocky compositions for the same reason.

Biodegradable polymers can be formulated into various shapes, such asfilms, strips, fibers, gels, meshes, sponges and spheres (such asnanospheres or microspheres). They can also be extruded, injectionmolded, compression molded, or solvent or spun cast. The primaryprocessing may also be followed by subsequent machining into finalparts.

The choice of shape is dependent on the cell therapy application. Forexample, if the biodegradable material is to be used only to cultureT-cells ex-vivo, but will be degraded so as not to be infused into apatient, the formulation of a matrix with high surface area ispreferred. Such a matrix would preferably simulate the structure ofdendritic cells in the lymph nodes, providing interconnecting star-burstlike structures or honey-combed structure shapes.

Microspheres are a preferred formulation because of the simplicity ofmanufacture and the spherical shape allows an increased surface area forinteraction with cellular receptors. Small microsphere particle sizes of1 to about 500 μm enables direct injection into the body by conventionalmethods. Thus the spherical shaped device can be used both for the cellculture and infusion steps of a cell therapy protocol. Nanospheres canalso be utilized, however, nanospheres do not provide enoughcross-linking to activate naive T-cells and thus can only be used withpreviously activated T-cells. In preferred embodiments, microspheresthat range in size from 1 μm to 10 μm are formulated.

According to the method of the present invention, the biodegradablesupport is first formulated into a shape, such as a microsphere. Thebiodegradable support is then coated with a first material providing areactive surface which is capable of binding to one or more secondmaterials. The second materials have a reactive surface which permitsbinding to surface structures on a cell. In preferred embodiments,second materials are capable of transducing a signal to a cell throughinteraction with a surface expressed cellular receptor.

In practice of the invention, the second materials can be first bound tothe first material on the biodegradable support and then mixed with thetarget T-cells, whereby the second materials bind to surface structureson the T-cells. Alternatively, the second materials can be first boundto the surface structures of the T-cells and the T-cells with the boundsecond material then mixed with the biodegradable support coated withthe first material. In both cases, the final mixture contains abiodegradable support coated with a first material, such first materialwhich is bound to one or more second materials, and such secondmaterials which are bound to surface structures on a T-cell.

The first material can be attached to the biodegradable support by meansof absorption, reactive groups, or by means of a coupling agent orlinker. The terms “coupling agent” or “linker” as used herein refer tobifunctional crosslinking or coupling agents such as moleculescontaining two reactive groups which may be separated by a spacer.

Suitable first materials are any biocompatible material capable ofbinding to a portion of the second material. Examples of suitable firstmaterials include polyclonal or monoclonal antibodies, or fragmentsthereof, and bioactive substances such as Protein A, avidin or biotin.In embodiments where the second materials are mouse-derived proteins,such as mouse antibodies, suitable first materials are polyclonalantibodies with specificity for the mouse immunoglobulins, such as sheepor goat-derived anti-mouse polyclonal antibodies or anti-mousemonoclonal antibodies such as rat-derived anti-mouse Fc antibodies. Inembodiments where the second material is coated with biotin, a suitablefirst material is avidin or an antibody specific for biotin.Alternatively, where the second material is coated with avidin, asuitable first material is biotin or an anti-avidin antibody. Inaddition, when the second materials are IgG molecules, the firstmaterials can be agents with high affinity for IgG, such as Protein G orProtein A.

First materials can be chemically coupled to the biodegradable supportwith glutaraldehyde or other di-aldehyde with or without the firstattachment of diaminoheptane spacer groups to the biodegradable support.Covalent bonding by nucleophilic displacement to biodegradable supportsactivated with tosyl groups (p-toluenesulfonyl), through cyanogensbromide activation or other similar methods can also be used. Thebiodegradable support could also be coated directly with avidin orbiotin to interact with a second material such as a mitogenic proteincoated with the opposite corresponding biotin or avidin.

Suitable second materials are biocompatible materials which are capableof binding to a cell surface structure. Preferably, the binding of thesecond material to the T-cell surface will transduce a signal to theT-cell when the second agent is immobilized or cross-linked by the firstmaterial. Signal transduction will have the effect of causing the targetT-cell to perform a fuinction desirable in cell therapy applications,such as proliferate, produce cytokines, differentiate and/or expresseffector molecules such as FasL, TRAIL and CD40L.

Examples of suitable second materials for use in the present inventioninclude agents such as synthesized compounds, nucleic acids andproteins, including polyclonal or monoclonal antibodies, and fragmentsor derivatives thereof, and bioengineered proteins, such as fusionproteins. In one example, the second materials are mitogenic proteins.Mitogenic proteins are two or more proteins that are able to deliver therequisite minimum of two signals to T-cells in order to cause theT-cells to become activated. Examples of mitogenic proteins are anti-CD3and anti-CD2 mAbs, in combination with a co-stimulatory protein such asand including proteins specific for one or more of the following T-cellsurface molecules: CD28, CD5, CD4, CD8, MHCI, MHCII, CTLA-4, ICOS, PD-1,OX40, CD27L (CD70), 4-IBBL, CD30L and LIGHT, including the correspondingligands to these surface structures, or fragments thereof.

Other suitable second materials include agents capable of delivering asignal to T-cells through cytokine receptors such as IL-2R, IL-12R,IL-IR, IL-15R, IFN-gammaR, TNF-alphaR, IL-4R, and IL-1OR, including mAbsto these receptors, fusion proteins with a reactive end specific forthese receptors and the corresponding ligands to these receptors orfractions thereof. Other suitable second materials include any agentcapable of binding to cellular adhesion molecules on T-cells such asmAbs, fusion proteins and the corresponding ligands or fractions thereofto adhesion molecules in the following categories: cadherins, ICAM,integrins, and selectins. Examples of adhesion molecules on T-cells are:CD44, CD31, CD18/CD11a (LFA-1), CD29, CD54 (ICAM-1), CD62L (L-selectin),and CD29/CD49d (VLA-4). Other suitable second materials include anyagents capable of binding to chemokine receptors, including those in theC-C and C-X-C categories. Examples of chemokine receptors associatedwith T-cell function include CCR1, CCR2, CCR3, CCR4, CCR5, and CXCR3.

In one embodiment of the present invention, the biodegradable supportmaterial is constructed from a linear polyester polymer containing amixture of lactic acid and glycolic acid. This class of polymers meetsthe requirements of biocompatibility and biodegradation into harmlessend products. These polymers, hereinafter referred to as PLGA, aredegraded by ester hydrolysis into lactic acid and glycolic acid. PLGAhas been shown to possess excellent biocompatibility. The innocuousnature of PLGA can be exemplified by the approval by the regulatoryauthorities, including the U.S. Food and Drug Administration, of severalparenteral delayed release preparations based on these polymers.Parenterally administrable delayed release products currently on themarket and based on PLGA include Decapepty™ (Ibsen Biotech), Prostap S®.(Lederle), Decapeptyl®, Depot (Ferring) and Zoladex® (Zeneca).

Copolymers of DL-lactate and glycolide, rather than L-lactate andglycolide, are preferred because they are amorphous when DL-lactate is amajor component, as opposed to semicrystalline when L-lactate is a majorcomponent. This property decreases the degradation time of the polymer.The inherent viscosity (abbreviated as “I.V.”; units are indeciliters/gram) of the polymer is a measure of its molecular weight.Preferably, the inherent viscosity of the polymer is from about 0.10dL/g to about 1.0 dL/g (as measured in chloroform), more preferably fromabout 0.10 dL/g to about 0.50 dL/g and most preferably from 0.10 to 0.30dL/g.

Suitable biodegradable polymer material is a 50/50 mixture ofpoly(DL-lactide co-glycolide). The polymer can be purchased fromcommercial suppliers such as Birmingham Polymers, Inc (Birmingham, Ala.)under the trade name Lactel®. The 50/50 DL-PLG product number 50DG020with a inherent viscosity of 0.15 to 0.25 dl/g is a preferred materialfor use in the present invention. Another preferred material is 50/50DL-PLG with an inherent viscosity of 0.32 to 0.44 dl/g manufactured byBoehringer Ingelheim (Ingelheim, Germany) under the trade name Resomer®RG 503. Another preferred material is Lactel® 50/50 DL-PLG productnumber 50D040 (Birmingham Polymers) with a 0.26 to 0.54 inherentviscosity. In other preferred embodiments, polymer end groups can beadded to the biodegradable polymers, such as monofunctional alcohol,water or alpha-hydroxy acid, or PEG in order to increase thehydrophilicity of the polymer and thus increase the degradation time andprovide active groups for covalent binding of first materials to thepolymer.

In a preferred embodiment, the 50/50 DL-PLG is formulated intomicrospheres.

Microspheres can be prepared by various known methods, including solventevaporation, phase separation, spray-drying, or solvent extraction atlow temperature. The process selected should be simple, reproducible andscalable. The resulting microspheres should be free-flowing and notaggregates in order to produce a uniform syringeable suspension. Themicrospheres must also be sterile. This can be ensured by a terminalsterilization step and/or through aseptic processing.

In a preferred embodiment, the solvent evaporation method is utilized toproduce the microspheres (McGinity and O'Donnell 1997). To producemicrospheres with this method, the hydrophobic 50/50 DL-PLG polymer isdissolved in a water-immiscible organic solvent to give a polymersolution. The solution is then added into an aqueous solution of asurfactant to form an emulsion system and stirred. The faster thestirring speed, the smaller the size of the microspheres. Microspheresare obtained by subsequently evaporating the solvent by continuousstirring, which can be under vacuum or heat.

The water-miscible organic solvents of the present invention need to benon-toxic to the body. Typical examples of organic solvents are membersselected from the group consisting of acetic acid, lactic acid, formicacid, acetone, acetonitrile, dimethyl formamide, dimethyl acetamide,dimethyl sulfoxide, dioxane, and N-methyl pyrrolidone and mixturesthereof. Preferably, the water-miscible organic solvent is a memberselected from the group consisting of acetic acid, lactic acid, N-methylpyrrolidone, or a mixture thereof. The water-miscible organic solventmay be used alone or in a mixture with water.

The aqueous phase can contain an emulsion stabilizer that is preferablysoluble in water and alcohol, is capable of increasing viscosity of thesuspending medium (water-miscible alcohol) when dissolved in the medium,is non-toxic to the body and causes no environmental problems. Typicalexamples of emulsion stabilizer solutions are: water-soluble syntheticpolymers such as polyvinylpyrrolidone, poly(ethylene glycol), andpoloxamer; cellulose derivatives such as hydroxypropyl cellulose andhydroxypropylmethyl cellulose, and preferably, polyvinylpyrrolidone andhydroxypropyl cellulose. The content of emulsion stabilizer in thewater-miscible alcohol is preferably within the range of 0.1 to about50% (w/v), and more preferably within the range of 0.2 to about 20%(w/v). The content of emulsion stabilizer can be varied according to theviscosity of the water-miscible alcohol needed.

According to the present invention, the water-miscible alcohol, whereinthe emulsion stabilizer is dissolved, is stirred at a temperature of 10about 80° C., preferably from 20 to about 60° C., and most preferably atroom temperature at a speed of 200 to about 20,000 rpm, preferably at aspeed of 800 to 1000 rpm. The polymer solution is slowly added to thewater-miscible alcohol wherein the emulsion stabilizer is dissolved, andthe mixture is stirred from 5 minutes to about 60 minutes. Stirring canbe continued for up to 5 hours to allow evaporation of the organicsolvent. The resulting microspheres can then collected by centrifugationand washed extensively. The washed microspheres are then ready forattachment of the first material.

The diameter of the microspheres prepared should preferably be withinthe range from 0.01 to 300 um, and more preferably within the range from0.1 to 100 um. and most preferably between 1 and 10 um. The particlesize (diameter of the microspheres) can be controlled by adjusting thestirring speed during processing, the viscosity of the water-misciblealcohol, and the viscosity of the polymer solution.

Post-coating of the biodegradable support with the first material can beaccomplished by a variety of standard methods depending upon the natureof the first material. For most applications where the first material isa protein, passive absorption techniques are adequate for proteinattachment to the biodegradable support. Other applications may requiredirect covalent attachment or covalent attachment through a linkinggroup, such as when using first materials with low affinity for thebiodegradable support, or use of first materials such as DNA, lectins,enzymes and drugs, or in applications where the biodegradable device isused in an environment where a material is used that will displace thepassively absorbed first material. Various schemes of modification tothe surface of the biodegradable support can be used to introduceapplicable functional groups for covalent protein immobilizationincluding: hydrolysis to form carboxylic groups (the immobilization iscarried out through the protein's amino groups using condensing agents),hydrazinolysis to form hydrazide groups (immobilization through thealdehyde groups of the glycoprotein's carbohydrate fragments oxidizedwith periodate), aminolysis with bifunctional amines (condensation withthe protein's carboxylic groups), modification with glutaric aldehyde(immobilization through the amino and sulfhydryl groups of a protein)(Ertl, B., F. Heigl, et al. (2000). “Lectin-mediated bioadhesion:preparation, stability and caco-2 binding of wheat germagglutinin-functionalized Poly(D,L-lactic-co-glycolicacid)-microspheres.” J Drug Target 8(3): 173-84. Muller, M., J. Voros,et al. (2003). “Surface modification of PLGA microspheres.” J BiomedMater Res 66A(1): 55-61. Tessmar, J., A. Mikos, et al. (2003). “The useof poly(ethylene glycol)-block-poly(lactic acid) derived copolymers forthe rapid creation of biomimetic surfaces.” Biomaterials 24(24):4475-86.). Proteins are known to satisfactorily retain their stabilityon such matrices.

After coating a first material to the surface of the biodegradablesupport directly or through a linker, it is desirable to blocknon-specific adsorption of proteins that may be present during cellculture or upon infusion to a patient. Any innocuous protein may be usedfor this purpose. Bovine or human serum albumin are desired blockingagents. In cases where the large size of the albumin obscures theactivity of smaller active first material proteins, glycine or smallpolypeptides can be used as alternative blocking agents.

If the biodegradable supports are formulated into particles of less than0.5 μm, the chemical aspects of the attachment to the biodegradablesupport will remain the same, but the mechanical aspects have to beadapted. Most protocols will utilize centrifugation to separateparticles from reagents used in the first agent attachment process.However, this is not practical for particles of sizes of less than about0.5 μm since most microcentrifuges cannot spin this size particles downwithin 30 minutes and extremely high G-forces are not recommended as itbecomes very arduous to resuspend the particles. In this situation,alternative separation techniques are indicated, such as dialysis orforced membrane filtration. Commercial kits that use hollow fiberfiltration techniques are also available for effective separation of0.1-0.5 μm. particles.

In one embodiments, first materials that are proteins can be bond to thebiological support material by adsorption with standard known methods.One method for adsorbing a protein to the biodegradable support wherethe support is formulated into microspheres is to suspend themicrospheres in 0.1M Borate buffer at pH 8.5, spin down and resuspendthe microspheres 2 or 3 times. The first material protein is thensuspended in the borate buffer and added to the microspheres. Themixture is mixed end-to-end for at least 4 hours and for up to 24 hours.The mixing is preferably conducted at 4° C. After mixing, themicrospheres are spun and the supernatant removed and analyzed forprotein determination. The coated microspheres are then resuspended in aphysiological buffer, such as phosphate buffered saline containing ablocking agent, such as 1-5% bovine serum albumen and/or 0.05% w/v Tween20.

The coated biodegradable supports can then be combined with the desiredsecond materials or the second materials can be bound to the targetT-cells and then mixed with the first material-coated biodegradablesupports.

During processing, it is necessary to minimize the presence of moistureto avoid excessive degradation of the biodegradable support byhydrolysis prior to use. To avoid hydrolytic degradation, extraprecautions during processing are necessary. Steps should be taken todry the biodegradable polymers during processing. Polymers can be driedby incubating the polymer at 80° C. for 24 h. Drying can also beaccomplished by vacuum drying or drying in a recirculating air dryer.Care must be taken when drying polymers above room temperature, as someamorphous compositions may fuse when the drying temperature exceeds theglass transition temperature.

The biodegradable devices are best packaged in small aliquots so thatthe material is used quickly once the package is opened. Packagingshould be in desiccated moisture proof bags. The devices can besterilized by a variety of methods such as storage in alcohol, gammaradiation or ethylene oxide gas. Biodegradable devices should not besterilized by autoclave as the high temperatures can cause degradation.

The devices of the present invention can also be stored by flashfreezing and then stored in liquid nitrogen and can also be lyophilizedprior to storage.

EXAMPLES

The following examples are included for illustrative purposes only andare not intended to limit the scope of the invention.

Example #1

Microsphere Preparation

The solvent evaporation method was used for preparation of microspheres.Lactel® (Birmingham Polymers, Birmingham, Ala.) 50/50 DL-PLG productnumber 50DG020 with a inherent viscosity of 0.15 to 0.25 dl/g was usedas the polymer. The DL-PLG powder was dissolved in 20 ml of methylenechloride to a final 5% DL-PLG w/v ratio. The 5% DL-PLG solution was thenadded dropwise to 125 ml of 2.4% hydroxypropylmethylcellulose in 0.1Mglycine/HCl buffer pH 1.1 under constant stirring at 1000 rpm at roomtemperature (25±2° C.). Stirring was maintained until completeevaporation of the organic solvent (about 3 hours). Microspheres werecollected by centrifugation at 1000 rpm, 5 min at 4° C. followed bythree cycles of washing with distilled water, filtered and driedovernight. The microsphere sizes ranged from 3.0 to 7.0 um with a CVmaximum of ≦10%.

Coating with First Material

Polyclonal goat anti-mouse polyclonal antibody was suspended in 30 ml ofPBS solution with 5% human serum albumen (HSA) at a concentration of 10ug/ml. This solution was used to resuspend the dried microspheres at aconcentration of approximately 2×10⁸particles per ml. The microspheresand the polyclonal antibody were mixed end over end at 4° C. for 8hours. The microspheres were then washed 3 times in PBS with HSA,filtered and dried.

Application of Second Material

For one group of experiments, second materials were added directly tothe goat anti-mouse antibody coated microspheres. For this purpose, a50/50 mixture of anti-human CD3 mAb and anti-human CD28mAbs at a finalconcentration of 10 ug/ml were prepared in PBS containing 5% HSA. Thissolution was then used to resuspend the coated microspheres at a finalconcentration of 2×10⁸ particles per ml. The mixture was vigorouslymixed end to end for 4 hours at room temperature, washed 3 times,filtered and dried overnight.

Results

Microsphere Size

In order to determine the size distribution of the microspheres, aaliquot of the spheres was analyzed by laser diffraction (Shimadzu LaserDiffraction Type Particle Analyzer) and by phase contrast microscopy.For laser diffraction studies, the microspheres were suspended in PBScontaining 0.2% Tween as a wetting agent. The mixture was sonicated for1 min and analyzed under stirred conditions to minimize aggregateformation. The distribution (after eliminating aggregates) indicatedspheres ranging in size from 4 to 24 microns with a mean of 7 microns.

Binding of First Material

In order to verify the coating of the first material, microspheresabsorption coated with goat anti-mouse polyclonal antibody was suspendedin PBS containing 1% HSA and stained-with a FITC-conjugated mouse IgGmAb. As a control, non-coated microspheres were stained under the sameconditions. The beads were then analyzed by flow cytometry. The coatedbeads showed intense staining indicating successful coating with thefirst material.

Example #2 Biological Effect of Second Materials

To determine the effect on proinflammatory cytokine production ofT-cells stimulated with the method of the invention compared to priorart stimulation methods, the following study was conducted:

PBL were isolated by Percoll gradient centrifugation from leukopacksobtained by apheresis of healthy donors. CD4+ T-cells were purified bypositive selection using anti-CD4 microbeads (Miltenyi Biotech,Germany). Cells were cultured in X-Vivo 15 (BioWhittiker) supplementedwith glutamine. Purified CD4+ cells were placed in 24 well plates andwere incubated with either goat anti-mouse coated microspheres coateddirectly with anti-CD3 and anti-CD28 mAbs in a 50:50 ratio (directmethod) or the cells were first labeled with the anti-CD3 and anti-CD28mAbs and then incubated with the coated microspheres. As a negativecontrol, unlabelled cells were incubated with polyclonal goat anti-mousecoated microspheres. As a positive control, cells were incubated withCD3/CD28 coated Dynabeads. All groups were adjusted to a bead:cell ratioof 3:1.

Purified CD4+ cells were placed in the wells at cell densities of0.5×10⁶ per ml. Concentrations of cytokines in the cell-freesupernatants after 72 hours was measured by ELISA.

The cytokine data represents the mean ±SD of six different bloodsamples.

Method IFN-gamma (pg/ml) TNF-alpha (pg/ml) Microspheres direct 1019 +/−36 695 +/− 98 Microspheres indirect 5859 +/− 29 4988 +/− 122 Dynabeadscontrol 1349 +/− 48  654 +/− 101 Negative control N.D. N.D.

These data show that the indirect method of the present inventionenhances the Th1 cytokine production from primary T-cells.

Example #3 Proliferation

CD4+ cells were prepared as described in the example above except thatthe cultures were continued for 9 days. Fresh beads and/or antibodieswere added every three days when the cultures were split to aconcentration of 0.5-1×10⁶ cells/ml. Cells were seeded in triplicate atthe beginning of each experiment.

Starting cell # Ending cell # Method (in 10⁶ cells) (in 10⁶ cells)Microspheres direct 1 25 Microspheres indirect 1 58 Dynabeads control 122 Negative control N.D. N.D.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A biodegradable device for activating T-cells, the device comprising:a biodegradable support; and a first material attached to thebiodegradable support, wherein the first material is an antibody capableof cross-linking more than one second material, the second materialcapable of binding to a T-cell surface antigen.
 2. The biodegradabledevice of claim 1 wherein the biodegradable support comprises collagen,gelatin, albumen or polysaccharides.
 3. The biodegradable device ofclaim 1 wherein the biodegradable support comprises aliphaticpolyesters.
 4. The biodegradable device of claim 1 wherein the secondmaterials have reactivity to T-cell surface antigens.
 5. Thebiodegradable device of claim 1 wherein the first material comprisespolyclonal or monoclonal antibodies, or fragments thereof.
 6. Thebiodegradable device of claim 1 wherein the first material is attachedto the biodegradable support with glutaraldehyde.
 7. The biodegradabledevice of claim 6 and further comprising diaminoheptane spacer groups.8. The biodegradable device of claim 1 wherein the second materialsinclude mitogenic proteins, monoclonal antibodies, fusion proteins andagents capable of binding to chemokine receptors.
 9. The biodegradabledevice of claim 8 wherein the mitogenic proteins include anti-CD3 andanti-CD2 monoclonal antibodies.
 10. The biodegradable device of claim 9and further including co-stimulatory proteins that are specific for oneor more T-cell surface molecules.